VoFi is able to leverage an enterprise's local network, which allows
an organization to have direct control over the quality of the access network. This would be impossible in a mobile environment. For example, working in a multi-story building can subject users to poor call quality
for a variety of reasons, for example working near an elevator shaft.
Using a mobile network means there is very little that can be done to
improve coverage other than move to another location. In a VoFi
deployment, additional coverage and capacity can be supplied simply by
adding relatively low-cost access points. In addition, a wireless LAN
offers much better performance to end-users who increasingly need to
converge voice and data. Basically, a 54 Mbps WLAN connection has a lot
more to offer an end-user than a broadband cellular connection with less
than 1 Mbps.

VoFi also provides considerable cost savings by pushing even more
enterprise voice traffic to the enterprise IP network. The cost benefits
of using the enterprise IP network instead of a traditional carrier is at
the heart of VoIP's widespread adoption and success on the wired side of
the network. For the same reasons, companies are now trying to drive as
many voice calls as possible to the IP network, including calls made from
a desk phone. This allows companies to control costs, ensure quality and
derive additional value from the existing network infrastructure.
  
While VoFi has some very obvious and compelling advantages, it is
important that CIOs and network managers don't get carried away by the
hype. Instead they need to ensure they fully understand the technical and
operational requirements of a successful VoFi deployment. Voice is a
fundamentally different technical animal than data; any variance in the
network can lead to poor call quality, dropped calls and one-way audio. In
a data deployment, small fluctuations in network quality are unlikely to
be noticed by end users. This leads to the single most common pitfall for
voice deployments today - adds voice to a wireless LAN originally designed
for data. Inevitably this approach leads to poor results. For voice to
work reliably an enterprise must design, deploy and manage the WLAN with
VoFi in mind.

A comprehensive site survey and network plan is an absolute must for any
VoFi deployment. It is almost impossible to expect a reliable end-user
experience without taking the time to design the network for the needs of
voice. A standard rule of thumb is to ensure that all areas are covered by
at least two wireless access points with a suitable signal (typically a
minimum signal of between -64 to -67 dBm).  Special attention should also
be paid to evaluating the quality of the physical RF environment as well
as the overall capacity needed to support both voice and data applications
at peak traffic times. Staff should also identify and implement a Quality
of Service (QoS) strategy to provide voice traffic with real-time priority
over data. This is of course, not an all-inclusive list, but rather an
important reminder that there are many things to think about and plan for
before voice is rolled out.

In addition to this planning, companies should also be prepared to
overcome voice problems as and when they arise. This means taking the time
to establish a methodology and toolkit for troubleshooting voice. When an
end-user experiences a problem with VoFi there are several potential
sources of the problem, it could be rooted in the user's phone, in the RF
environment, a problem with the WLAN itself or there could be a QoS
problem caused by the competition of voice and data on the network. Once
identified, problems can be easy to resolve, but it is critical that
technical staff have the tools and understanding to quickly diagnose these
problems without having to go to the phone or WLAN vendor. Regardless of
the tool of choice, it is important that staff is prepared for problems
and that a policy is agreed regarding problem resolution.

Chris Roeckl is vice president of marketing at AirMagnet, the leading
provider of wireless security and performance management solutions. He has
more than 20 years of experience dealing with networking products and
solutions.